The use of hybrid inflators for the inflation of air bags in automobiles is well known. Typically, a hybrid inflator includes a rupturable burst disk which releases a flow of gas from a pressure vessel in which the gas is stored to an air bag for inflation thereof. Rupture of the burst disk is responsive to a vehicle condition such as a collision.
In certain hybrid inflators, an igniter assembly is provided which, when actuated, ignites a body of pyrotechnic material. The ignited pyrotechnic material heats and pressurizes a stored inflator gas. The heated and pressurized stored inflator gas is then released for air bag inflation by rupture of the burst disk.
In the prior art, it has been proposed to use a gaseous hydrocarbon as part of the stored inflator gas. In U.S. Pat. No. 5,263,740, a hybrid air bag inflator is disclosed which includes a metal container having a sealed chamber. The sealed chamber contains a mixture of gases including an inert gas, a flammable fuel gas and an oxidizer gas. In conjunction with the metal container, an ignitable material is provided which is ignited by a squib. Ignition of the ignitable material releases the gases in the sealed chamber for combustion of the flammable fuel gas portion thereof for air bag inflation.
U.S. Pat. Nos. 5,350,192 to Blumenthal, 5,344,186 to Bergerson and 5,348,344 to Blumenthal et al. also disclose hybrid-type inflators utilizing a mixture of a fuel gas and other gases.
These types of hybrid inflators are not without their drawbacks. Since the gaseous hydrocarbon is combined with an inert gas and an oxidizer gas, it is difficult to realize uniform ignition of the combustible portion of the stored gas. In addition, these prior art inflators tend to be bulky in size and weight due to the presence of a manifold or plenum which receives the released stored gas prior to air bag inflation. These prior art devices also tend to be complex in design. In addition, solid particulate levels in the gas may be at unacceptable levels due to ineffective combustion.
In view of the drawbacks of these prior art hybrid inflators, a need has developed to provide an improved hybrid inflator which reduces solid particulate levels in the effluent gas when inflating air bags and also provides increased flexibility in inflator performance. In addition, a need has developed to provide inflator designs which are lighter in weight, simpler in design for weight savings when used in automobiles and lower in manufacturing costs.
In response to these needs, the present invention provides a hybrid inflator which utilizes a gaseous fuel in a first pressure vessel with a second pressure vessel storing a compressed inflator gas such as air, a mixture of argon and oxygen or mixtures thereof.